1. Field of the Invention
The present invention relates generally to personal audio listening devices which are worn by individual listeners and to methods related thereto. More particularly, the present invention is directed to a bone conduction audio listening systems and methods.
2. Related Art
Most conventional personal audio listening systems do not use bone conduction. Instead, such conventional systems provide sound to the listener in a normal air conduction fashion via the ear canal. These conventional personal sound systems have been marketed for use by listeners engaging in, among other things, outdoor activities such as jogging, hiking, skiing, and bicycling, and indoor activities such as housework, painting, and relaxing.
A well-known conventional sound system of this type includes a tape recorder/player or radio with a set of headphones or earphones connected by suitable wires to the radio or tape player. The headphones or earphones generate sound which is provided in an air conduction fashion to the listener by the ear canal(s). While such a system may provide high-quality audio for the listener, several serious disadvantages for the listener exist. Among these is the disadvantage of blocking ambient sounds in the local environment. Such ambient sound blockage may result in serious accidents for the listener due to the inability to hear local sounds.
Another serious disadvantage of this conventional personal audio listening system concerns the potential loss of hearing to the listener. Several medical studies specifically show that usage of such a conventional personal audio listening device leads to permanent hearing loss. See, for example, P. J. Catalano, S. M. Levin, "Noise-Induced Hearing Loss and Portable Radios with Headphones," International Journal of Pediatrics Otorhinolgryngology, 1985, p. 59 Tufts-New England Medical Center, "Stereo Earphones and Hearing Loss," The New England Journal of Medicine, Dec. 1982, Vol. 307, No. 23; and, P. C. Lee, M.D., C. W. Senders, M.D., "Transient Sensorineural Hearing Loss after Overuse of Portable Headphone Cassette Radios," Otolaryangology, Head and Neck Surgery, Vol. 93, No. 5, which references are incorporated by reference herein.
Other conventional personal audio listening systems are available which overcome some of the aforementioned safety and hearing loss problems by eliminating the headphones; however, they tend to be bulky, cumbersome, and uncomfortable to wear.
Examples of such conventional personal audio listening systems without headphones are shown in: U.S. Pat. No. 4,589,134 to Waldron for a sound system enclosed in a vest meant to be worn by the listener; U.S. Pat. No. 4,070,553 to Hass, for a scarf-tube enclosing a sound source meant to be worn around the listener's neck; U.S. Pat. No. 3,869,584 to Wilde, covering a device enclosing the ears of the individual listener; and U.S. Pat. No. 3,868,572 to Kaufman et al., representative of personal audio devices worn inside the ear of the individual listener. Yet another conventional personal audio system includes speakers adapted to clip onto a person's clothing, as shown in U.S. Pat. No. 4,322,585 to Liautaud.
Turning now to conventional bone conduction audio devices, they are typically hearing aids for the hearing impaired. Examples of such bone conduction hearing aids are found in: U.S. Pat. No. 2,230,500 to Lybarger; U.S. Pat. No. 2,258,638 to Zarth, West German Pat. No. 2451977 to Breckwoldt, and United Kingdom Pat. No. 743,722 to Patch. Most modern bone conduction hearing aid devices include the ability to implant the bone conduction oscillator beneath the listener's skin in direct contact with the mastoid bone. Such a device is shown in U.S. Pat. No. 4,612,915 to Hough et al.
The disadvantages of conventional bone conduction hearing aid devices generally include bulky and unsightly components designed to transmit a narrow band of audio frequencies, usually in the human voice range. Such narrow frequency range is unacceptable for musical listening purposes. Bone condition hearing aids are typically used in two circumstances: structural anomaly and chronic ear disease. If the ear is malformed or if there is no ear canal to channel air conductive sound, then the use of bone conduction is mandated. In addition, due to hearing impairment, such conventional bone conduction hearing aids must generate sounds at very high levels in order for the listener to be able to adequately "hear" by bone conduction action the sounds that are being emitted.
All bone oscillators rely on pressure to ensure good contact with the mastoid. Inadequate contact with the mastoid results in the hearing impaired listener from being unable to "hear" by bone conduction the sounds being emitted. This pressure needed for the required good mastoid contact may be achieved by mounting the oscillator on a headband, incorporating it in the temple portion of eye glasses, mounting it on the mastoid bone with tape, or designing some special system for maintaining mastoid contact. Such special contact includes both the subcutaneous attachment described in the U.S. Pat. No. 4,612,915 to Hough et al., noted above, and devices mounted within or on the teeth as shown in U.S. Pat. No. 3,985,977 to Beaty et al.
While these conventional systems, both bone conduction and air conduction, may function satisfactorily for their intended purposes, there is a need for a portable individual audio listening system which is comfortable and safe to use in a wide variety of activities that cannot be accommodated by the conventional systems. The inventor believes that the ability to hear ambient sounds is important to many listeners engaged in disparate activities. It is, of course, advantageous for joggers, runners, and cyclists to hear approaching traffic or warning signals for safety reasons. It is also advantageous to allow the individual listener to be able not only to listen to their local environment, but also to be in audio contact with remote communication centers, such as found in public utility work, military operations, and in the health care field.
Conventional audio listening systems have been developed which overcome the above-noted safety issues, but accomplish this at the expense of individual listener comfort. Other conventional audio listening systems have been developed that have addressed the comfort issue at the expense of listener hearing loss. In addition, none of these conventional devices utilize bone conduction methodology to provide high-quality audio, which is safe and easy to use, lightweight, waterproof, attractive, and comfortable.